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Cataract -- A Major Blinding Condition

Of the four diseases of greatest concern to the World Health Organization (WHO) Program for the Prevention of Blindness--trachoma, onchocerciasis, xerophthalmia, and cataract--cataract alone is the leading cause of blindness in all countries of the world. Cataract is the leading blinding condition in the 116 countries covered by the Blindness Data Bank* in the WHO Program for the Prevention of Blindness. An estimated 42 million people are affected by severe loss of vision, and cataract causes 17 million of these losses. Cataract was indicated as the prime cause of blindness in 43.6% of country reports and accounts for 30%-50% of blindness in approximately half the reports in which relative blindness prevalence is indicated. It is especially prevalent in developing countries of the tropical belt.

Developing countries indicate cataract as the major cause of severe visual impairment. Cataract frequency differs greatly in different geographic areas. A population-based prevalence survey for blindness (defined as visual acuity less than 3/60), carried out with WHO assistance in various African areas not endemic for trachoma or onchocerciasis, revealed a blindness rate of approximately 1%, with cataract accounting for 40%-50% of visual loss. However, analysis of data from a blindness survey of Australian aborigenes indicates an increased cataract rate in cases of severe trachoma scarring.

Senile cataract appears to have earlier onset in certain areas in Africa than in other parts of the world, with incidence becoming significant in the 40-50-year age group. A recent report from Asia indicated that, in a certain population group in Nepal, cataract apparently starts at about 35 years of age. In one region of India, with a total cataract prevalence of 4.3% for all ages, a prevalence rate of 1% was revealed for the 30-49-year age group and increased markedly to 67% for ages 70 and older. *WHO. Weekly Epidemiological Record 1982;57:145-6.

A WHO-assisted survey of blinding conditions, carried out in several areas of Africa and Asia, detected cataract blindness in 0.3%-4% of the population. Age-specific prevalence of blindness due to cataract rose steadily, starting at 45 years of age. In a survey in North Africa, cataract contributed to blindness in 0.3% of the total population, in 2% of those aged 41-60 years, and in 11.6% of those aged over 60. Cataract is expected to become even more prevalent with the general increase in life expectancy. In developing countries, the estimated 13 million persons who are blind due to cataract may reach 30 million by the year 2000 unless efficient, full-scale treatment programs reach all rural areas.

The present WHO strategy to combat blindness from cataract is based on simple ocular surgery, which, in certain peripheral areas, is not adequate to keep up with new cases or with the backlog of cases. Because of the rapidly increasing impact of cataract, research on possible prophylactic measures is gaining attention. Reported by WHO. Weekly Epidemiological Record 1982;57:397-8.

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